This invention relates to cementing casing in well bores drilled in subterranean formations. In particular, this invention relates to methods for cementing casing in a well bore without surface casing or a well head.
Typically, prior to cement operations, a relatively larger diameter surface casing is run into the well bore to a relatively shallow depth. A casing string is then inserted in a well bore. Circulation fluid fills the inner diameter (“ID”) of the casing and the caseing-by-well bore annulus. For purposes of this disclosure, “circulation fluid” is defined as circulation fluid, drilling mud, formation fluids and/or any other fluid typically found in pre-cemented wells. Once the casing is run into the well bore, it is desirable to flow a cement composition into the annulus and allow the cement composition to harden to completely seal the annulus and secure the casing in the bore hole.
However, in some well bores, no surface casing is installed prior to insertion of the casing string. FIG. 1 illustrates a cross-sectional, side view a well bore 1 and casing 3. An annulus 5 is defined between the well bore 1 and the casing 3. At the lower end of the casing, a casing shoe 4 is attached for circulating fluid between the annulus 5 and the inside diameter of the casing 3. The well bore 1 is filled with a circulating fluid such that an annulus circulation fluid surface 6 is at approximately the same depth as an ID circulation fluid surface 10. A reservoir 7 is located proximate to the well bore 1. Also, a truck 9 is parked in the vicinity of the well bore 1. As illustrated, the casing 3 simply protrudes from the mouth of the well bore 1 without a surface casing or a well head. Thus, FIG. 1 simply illustrates an open well bore with casing sticking out of it.
Well configurations as illustrated in FIG. 1 present additional challenges for conducting cementing operations. For example, cementing of these wells is problematic because there is no well head forming a seal of the annulus, there is no well head providing nipple connections for fluid communication with the inner diameter of the casing or the annulus, and there is increased risk of well bore cave-in.